7610 hydraulic lockup

[luvbug]

Has any body had a problem with their hydraulics locking up? The other day while doing some loader work I went to lower the FEL bucket and nothing happened, I moved the loader control around and still nothing. I ideled down and checked all the control levers to make sure I didn't knock anything in / out of gear and everything was O.K. I checked the 3PH control and it was all the way foward, PTO not engaged. I ran the rpm's back up and the loader went up but not down. I checked the BH and it started to extend, OK, but it would not contract. I ideled back down and shut down the tractor, checked the hyd. oil, OK, looked everything over, no problems anywhere noted. Started it back up and the problem still existed. Shut down again and I was able to lower everything thru the bleed down when moving the control levers. Started back up and parked it in the garage. Double checked everything again and again everything went up but not down. Two days later went to check on it and everything works fine???? Wierd??? Anybody else experience this? Called the dealer, he's picking it up in 5 days to check it out and do the 50hrs service. Any comments are appreciated.

 

[DanR67]

luvbug -

I checked my B7610 Kubota Workshop Manual - the FEL and BH are not included (must be separate WSMs) - but I did look over the hydraulics & troubleshooting tables. Your symptoms had me perplexed before I even opened the manual!

Some things to think about:

1) The FEL hydraulic attachment point is in series with (in-line / before) the 3PH lift control - so if the hydraulic pump were the problem - then the 3PH shouldn't work either. However - since you could RAISE the FEL - that clearly indicates you have pressure....

The hydraulic pump is an internal gear type - it runs continuously in proportion to the engine speed. The hydraulic pump is actually a "double-pump" - a 2nd gear pump (lower flow capacity) running off the same drive shaft supplies the power steering exclusively. If the hydraulic pump shaft had failed - then you would have had no power steering either.(think VERY expensive shear pin!)

My experience (13+ yrs industrial hydraulics) with gear pumps is that they are extremely durable and can take quite a beating. (The HST "variable pump / motor" is more complex and needs a bit of care - just keep up with the scheduled fluid changes)

2) The WSM asks if there is "noise" or "no noise" when attempting to move the implement? "No noise" clearly means no hydraulic oil is going anywhere - I'd think the "whine" ("noise") of the hydraulics would have changed if the cylinders were working - but "struggling against" a blockage.

3) Was the raise speed of the FEL / BH *normal* - or was it "slower than normal"? (As your complaint is "lock up" - I assume it isn't faster in any case! /forums/images/graemlins/wink.gif )

Slow in one direction / no movement in the other suggests that the spool of the control valve could be jammed / mechanically limited - but this falls apart IMO - because you have two different implements / control valves acting the same way?!?!

4) If the hydraulic pressure relief valve were stuck open - you should not have had pressure to raise the FEL / BH!

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So where does that leave us? Assuming the pump is OK (pressure to lift FEL / BH), and it is unlikely that two separate control valves jammed in the same way / at the same time - my guess would be some kind of stuck check valve in the return / tank line of the cylinders - especially if the hydraulics are shared between FEL & BH.

I'm not entirely thrilled with this explanation either - as the FEL for example - uses the "small side" of the hydraulic cylinders for lifting the bucket - so the lowering side has the bigger piston / surface area ( = more force --> that's why you can lift the front tires easily when you apply "downforce") - which should mean that it would be easier to force open a stuck check valve when LOWERING the FEL - if that were the problem....

Sometimes check valves are "pilot controlled" - meaning that some other device *decides* whether the check valve is allowed to open - not just the flow / pressure of the oil passing through the check valve itself.

If the "pilot controlled check valve" theory is correct - this would explain why the FEL / BH could be lowered with the engine off: the "pilot pressure" to hold the check valve CLOSED is missing.

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Glad to hear that everything is working again - I'd sure like to know what the dealer says - an interesting problem to say the least! /forums/images/graemlins/confused.gif

Hope that my ramblings help,

Dan

 

[DaGoatMan]

It happened to me once on my B7610, but corrected itself after 10 or so seconds of moving the joystick around in different directions. Has only happened once in 25 hours of operation. Figured it was just a glitch. Will pay more attention to it if it happens again. Thanks for sharing your experience.

 

[v8dave]

A B7610 with a Kubota a front end loader and a Kubota backhoe are on two completely separate hydraulic systems. If they are on the same hydraulic system, I assume you have a non-Kubota backhoe.

You might have had air in the system. Recently, on my tractor with the engine off and the BH bucket full of rain water, I pushed the BH bucket down and out (from the stow position) with my foot, while holding the valve open. The water emptied out but the bucket wouldn't stay extended.

The next day, I used the BH and had difficulty with the BH bucket curl control. It wouldn't work either way. I thought it might be air in the lines from my foot push. I operated the boom and dipper several times and tried the bucket curl again. This time the bucket curl worked fine. I just marked it up to air in the lines/valves.

Check your hydraulic fluid level, the little yellow stick under the seat. If you are slightly low on fluid and were not on level ground, you may have sucked some air into the system and had trouble purging it.

 

[ChuckinVA]

I have had this problem with my b7610 with the loader. I spoke to the dealer about it and they thought it might be the detent ball in the loader control. They said they sometimes get a flat spot on them and have to be replaced. Mine only had 20 or so hours when it happened. I have had it happen a couple of other times but always clears after I move the controller around